1. Technical Field
The present invention relates to a mounting component, an electronic device, and a mounting method.
2. Related Art
In various mounting components such as a semiconductor element and a micro switch, a metallic leg portion is soldered to and mounted on a pad formed in a conductive pattern of a printed circuit board. Recently, due to miniaturization of a device, sizes of the leg portion of the mounting component and the pad of the conductive pattern are reduced, and array pitches of the leg portions and pads also become narrowed. Therefore, a bonding area between the leg portion and solder is reduced to cause mounting strength of the mounting component to become insufficient to the conductive pattern.
Particularly, in mounting components such as a micro switch and a connector, the higher mounting strength is required because a relatively large external force is applied to the soldered leg portion in use. In the mounting components such as the micro switch and the connector, frequently the soldered leg portion and a spring constituting a contact mechanism are integrally formed, and occasionally it is necessary that the leg portion be made of a material having not very high affinity with the solder, which results in peel-off of the solder.
The mounting strength is enhanced when the amount of solder used is increased to enlarge a wetted area. However, when the amount of solder is excessively increased, the solder runs over each pad, which results in the adjacent pad's short-circuit. When the solder is melted, a flux contained in the solder flows out to run up the leg portion. Therefore, in the mounting component such as the micro switch and the connector which is not completely molded, when the used amount of solder is increased, the flux invades into the mounting component to generate a trouble such as contact failure of the contact.
For example, as disclosed in FIG. 3 of Japanese Unexamined Patent Publication No. 2002-334964, in a technique of enhancing the mounting strength, the wetted area of the solder is enlarged to enhance the bonding strength by providing a vertical hole 6 or a groove 5. The vertical hole 6 or the groove 5 is opened to a bottom surface of a leg portion of a soldered lead 3, and sucks up the solder by capillarity. However, in the mounting component such as the micro switch and the connector to which a large external force is applied, joining strength between the leg portion and the solder is insufficient even if the vertical hole of Japanese Unexamined Patent Publication No. 2002-334964 is made.
Particularly, in a mounting structure of Japanese Unexamined Patent Publication No. 2002-334964, an inner circumferential surface of the vertical hole is perpendicular to a conductive pattern, and is extended in a direction identical to that of an outer circumferential surface of the leg portion.
Therefore, when a force is applied to the leg portion so as to perpendicularly tear off the leg portion from the conductive pattern, a shear force is applied among the inner circumferential surface of the vertical hole, the outer circumferential surface of the leg portion, and the solder to generate slip in a bonding surface, whereby frequently the leg portion is easily pulled out from the solder.